Improvements cobalt electroplating



used.

LIN-Iran STATES PAT NT omen;

a s o DAMs, JR, or BOSTON, MASSACHUSETTS.

IMPROVEMENT IN COBALT ELECTROPLATlNG.

Specification forming'part of Letters PatentNo. 172,862, dated February1, 1876; application filed v January 17, 1876. I v

shows that various experiments have been:

made by electro-metallurgists in the electrodeposition of cobalt;.and sofar as these experiments or processes are described in the books, itappears that allusions to such deposits have been made as early as 1844,andsince that date reference to the same subject may be found in theworks of Since, Becqu'erel, Ellsner, and Gore.

Gore (1860) simply mentions thesolution of the chloride of cobalt as onewhich may be Ellsner (Leipsic, 1851) recommends the cyanide of cobaltand potassium. Becquerel, in a note printed in the Oomptes Rendus of theFrench Academy for July, .1862, states that he has obtained 'a gooddeposit from the neutral chloride of cobalt. Smee, in his work onelectro-metallurgy, (London, 1844,) in a measure contradicts Becquerelas to the chloride of cobalt, and recommends the solution of thechloride of cobalt with excess of ammonia. He says: cobalt may bereduced from its chloride, to which excess of ammonia has been added, byusinga cobalt positive pole connected with a series of batteries, whenthe deposition will take place upon the negative plate, which mayconsist of copper.

The reduced metal is white, but it is not thrown down freely. Thechloride of cobalt alone seems only to yield an oxide at the neg-' ativepole. The cobalto-cyanuret of potassium, formed by digesting oxide ofcobalt in the cyanurct, yields, by decomposition with a compoundbattery, some metal, but hydrogen 7 has a great tendency to be evolvedfrom this solution.

exigencies of his art. I have found. that a solution made and used inthe manner described in the books will not produce such a continuous anduniform deposit of cobalt as is necessary for the successful andpractical electroplating of metals with cobalt, and that if theelectroplater follows the directions given in the books he not only willbe unable to produce successful practical cobalt-plating,

but in some cases will bring his solution into I such a condition as toprevent any useful deposit of cobalt.

I .have found, further, that the simplesalts of cobalt, such as arerecommended by Bee querel and others, are not such salts as can .be usedin the practical electroplating with cobalt, and this I find to be trueeven if they are prepared from pure cobalt.

I have found out, also, that the simple saltsof cobalt, whenassociatedwith another electrolytesnch as the vchloride of ammonium, orthe sulphate of ammonia, or the chloride of magnesium, or the sulphateof magnesiacan be used so as to produce good results in practicalcobalt-plating; and I find that no good results can be obtained exceptby the use of a simple salt .of cobalt in combination with some otherelectrolyte of the alkalies or alkaline I have found that the best ofsuch combined salts are, the chloride of I cobalt and ammonium, thechloride of cobalt and magnesium, the sulphate of cobalt and ammonia, orthe sulphate of cobalt and magnesia. 1

I have found, further, that, in order to produce the best results, thecobalt solutions place in solutions in which exist salts of alkaliessuchas the nitrates of soda or potash, or free nitric acid-and the reason ofthis, I believe, is, that wheiithese salts are present in the solutionsin appreciable amount potash and soda are eliminated in the actual useof the solution simultaneously with the deposit of cobalt, and thus thedeposit is rendered worthless for the purposes ofthe electroplater. Suchsalts of alkalies, and likewise free acid, are, liable to exist in thesolution when used, either because they have been introduced therein inthe process of making, or because they are introduced or formed thereinin the actual using of the solution.

I have now stated, in general terms, the process which I find to be thebest for practical cobalt electroplating.

' In order to enable a person skilled in the art to practice the processof cobalt electroplating so discovered by me,I give the following as amethod by which he can make the necessary solutions and anodes. Purecobalt is not found in the market, as there is no commercial demand forit, and therefore, in mostinstances, a cobalt solution would be madefrom black oxide of cobalt, which, in the state in which it is found incommerce, contains as impurities copper, arsenic, tin, iron, andmanganese, or some of these substances, which it 1 is necessary toeliminate. Proceed as follows; Dissolve a given weight of the oxide ofcobalt in hydrochloric aci'd.- To this solution add, for every pound ofoxide used, a half, pound of the chloride of ammonium. Then filter thesolution, it necessary, and to it add "sufficient ammonia to render thesolution strongly ammoniacal. Then allow this ammoniacal solution tostand, with occasional brisk stirring, until it becomes of a wine-redcolor. Then add an excess of commercial murij atic acid, and raise thewhole to the boilingred'heat in a crucible or other suitable vessel, 1and a chloride of cobalt will be produced practically free fromimpurities.

To produce the chloride of cobalt and ammonium, make a solution bydissolving three ounces of the chloride of cobalt and two ounces of purechloride of ammonium to each gallon of the solution.

To produce a solution of the chloride of cobalt andmagnesium, make asolution as above, substituting chloride of magnesium for the v-chlorideof ammonium.

To produce a solution of the sulphate of co balt and ammonia, dissolvethe chloride of cobalt inwater, and for every five parts of such drysalt add four parts, by weight, of sulphuric 1 acid and evaporate 'todryness; redissolve in; water and add five parts of pure sulphate of 3If there should be an excess of acid,

ammonia. neutralize with ammonla.

To. produce the sulphate ofcobalt and mag- I do not claim the processesof making these solutions as my invention, and in no way limit myinvention to the'iprecise chemical processes by which these solutionsare produced ready for use.

The solutions, when made as above described, will mark from 6 to 7 Baum,though much weaker solutions may be used, and even stronger ones, ifdesired.

I do not confine my inventio n to the particularproportions of each saltcontained in the solutions above described, forthe proportions of eachsalt may be varied in any given solution. I have given theaboveproportions of these saltsas those which I prefer.

The method for producing a suitable anode to be'used with thesesolutions is as follows: Precipitate the chloride of cobalt with potash;soda, or carbonate of ammonia then makea solution of tartaric acid,about three partsof acid to two parts of dry chloride, and add to it themoist oxide of cobalt, and raise the whole to the boiling-point. Atartrate of co balt is formed, which throw uponthe filter and washseveral times with boiling water, dry, mix with a little lamp-black orother suitable form of pure carbon, and heat to whiteness in a closedHessian or other suitable crucible. The tartrate of cobalt is thusreduced to the metallic state and fused, and can then be readily castinto plates or anodes of any desirable form. r

After the solutions and anodes have been prepared as herein described,cobalt may be readily and continuously deposited; but in order to carryon the deposition of cobalt continuously it is necessary to observecertain pre cautions. First, great care should be exercised, inpreparing the work for plating, that none of the acid or alkaline dipsshould be introduced' into the solution. Second, anot too highbattery-power should be used a strength of current of two Smee cells issufficient.

In plating articles of zinc with cobalt it is first necessary to coatthem with copper.

Having thus describedmy invention of improved processes ofelectroplating with cobalt, I claim-- v I i 1. In the electro-depositionof cobalt, the

use of a solution of a simple salt of'cobalt,

combined with another electrolyte, consisting of a salt of the alkaliesor alkaline earths, substantially as described' v 2. The use, in theelectro-deposition "of cosium, or sulphate of cobalt :andammoniayor 3the sulphate of cobalt and magnesia, substantially as described. .j

alkaline, substantially as described. Y

I 3. The use,.in th'e-eleetro-deposition of cobalt;iwhich consists'inconvertingthe -chlohalt, of a neutral solution, neither acid nor ride orother salt of cobalt into the tartrate,

mixing this with carbon, heating to reduc- .4. The use, in theelectro-deposition of co tion, and finally casting, substantially asdebalt, of solutions of cobalt, in the manner described. scribed, so asto be at alltimes' during the op- I eration free from the presence ofsoda, potash, Witnesses: or nitric acid, or either of them. E. N.-DIGKERSON, J r.,

"ISAAC ADA s n.

5. The process of making an-anode of co- JNO. RrLEFFERTs.

